A technique of detecting illuminance using a solid-state imaging element such as a CMOS image sensor has been conventionally proposed. For instance, a camera module can adjust the brightness of a display screen in accordance with the detected illuminance. A method of adding up a luminance value detected at each pixel and taking an average of the luminance values in an entire imaging screen as an illuminance value is known for the method of detecting the illuminance by the solid-state imaging element.
When using the luminance value of the entire imaging screen, luminance data, which is considered a disadvantage in the calculation of the illuminance value, may be contained. For instance, if a subject having low reflectivity such as a shaded portion or a black subject is contained in great amount in the imaging screen, the reflected light to be received by the solid-state imaging element reduces and the illuminance value lower than the actual value may be calculated. If a direct light from a light source such as a spot light is entered, the illuminance value higher than the actual value may be calculated. Furthermore, the illuminance value lower than the actual value is sometimes calculated if saturation of the output with respect to the incident light quantity occurs in the solid-state imaging element.